This video from "Tutorials for the Calculus Phobe" will help introduce the important things for Concept 8.
This lesson will cover the "long way" of evaluating limits at infinity, which helps to explain the "shortcut way" you have already learned.
*EVEN IF YOU UNDERSTAND THE SHORTCUT WAY ALREADY, you MUST also understand and be able to explain the long way, so watch this video!!!**
Source: Created by Crystal Kirch using Camtasia for Mac